This invention is disclosed in Disclosure Document No. 419672, filed May 19, 1997 with the US Patent Office.
1. Field of the Invention
This invention relates to transducers, and in particular, relates to a spiral wound transducer having an array of metallized plastic capacitive force cells.
2. Description of the Related Art
Transducers are devices which convert one form of input energy to a different form of output energy. Thus, electromechanical transducers may convert electrical energy to mechanical energy, due to the electrostatic attraction caused by two opposing and oppositely charged plates which move together in response to a voltage applied between the plates, converting the input electrical energy to mechanical energy.
Integrated force arrays (IFAs) are planar, thin film membrane actuators that act as transfer devices for electrostatic force. They are capable of large amplitude motion and are capable of significant work per unit volume. FIG. 1 (a-d) shows the cross-section of a prior art IFA without (FIG. 1a) and with (FIG. 1b) an applied power supply 20, as well as a perspective view of the IFA without (FIG. 1c) and with (FIG. d) an applied power supply. Devices which use IFAs as drivers to scan lead zirconium titanate (PZT) ultrasound acoustic imaging transducers are discussed by Bobbio et al. (Proc. SPIE Conf. on Smart Structures and Materials, 2733:123 (1966)).
Many types of previous transducers consume substantial amounts of electrical power. For example, electromagnetic devices like solenoids consume electrical energy when they are energized but not moving (at a control point of the motion). The IFA device and the spiral wound transducer (SWT) device of the invention consume energy only when they are moving and not at the control points. Further, both the SWT and IFA devices can operate silently and in a muscle-like way where the extent of deformation is controlled in a proportional way by the amount of voltage applied. In the case of the IFA, the height of the capacitor plates (H in FIG. 1d, discussed in more detail below) is limited by the ability to pattern a high aspect ratio feature in a thin plastic film. The aspect ratio of the IFA feature is the ratio to the capacitor gap (1 xcexcm). Practically, the processing has proven to be limited to an aspect ratio of 2, and thus, H is approximately 2 xcexcm. In distinction to an IFA, aspect ratio considerations do not limit the dimensions of the capacitor plates in the SWT. The prototypes for the SWT are about 2 mm vs. the IFA""s 2 xcexcm, or a factor of 1000. Since the force is proportional to this dimension, the SWT""s are 1000 times stronger.
It is therefore an object of the invention to provide a transducer which, like the IFA, is energy efficient, silent and capable of proportional response, but whose force is not limited by the thickness of the layer being patterned (H in FIG. 1d for the IFA).
Other objects and advantages will be more fully apparent from the following disclosure and appended claims.
The invention herein is a transducer compressible in response to electric power, comprising a flexible, conductive plastic layer microimprinted with a pattern; and a stiff plastic layer containing a conductive embedded sheet. The transducer may be formed by winding the flexible layer and the stiff layer together around a central form. In some versions of the invention (e.g., as shown in FIGS. 8-11), the flexible and stiff layers may be joined together before winding.
Other objects and features of the inventions will be more fully apparent from the following disclosure and appended claims.